The thing that confuses me is that all the people I know who do this, count the hours by the clock rather than the halachic time. This includes following the clock with time zones, and daylight savings. So, regardless of whether Shabbos starts at 4:30 or 8:00, they will avoid kiddush between 6 and 7.

My question is, does this make any sense at all? Is there any source for following the clock? Furthermore, even if we do follow the clock, can there be any reason to follow daylight savings time?

1 Answer
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There are a few things that are not affected by Shaos Zemaniyos. Waiting time between eating meat and milk - you wait the amount of actual hours your Minhag is. Mazalos are also not affected by Shaos Zemaniyos and the Mazal of Maadim is between 6-7 PM during standard time and between 7-8 PM during daylight time.

Please see this link from Medrash Shocher Tov which quotes a Rashi in Rosh HaShana 11b1 that Mazalos are not based on Shaos Zemaniyos.

Okay, but this just explains that it's a full clock hour, six hours from local mean solar noon. That still doesn't tell us, for example, that it shouldn't be affected by Daylight Savings Time (i.e., that it should be 6:00-7:00 during the summer rather than 7:00-8:00 - or actually, in New York, four minutes before the hour).
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AlexNov 23 '11 at 21:01

Although we have no minhag with regards to not making Kiddush at a certain time, in Breslev we do use standard hours to calculate the correct time for Tikkun Chatzos.
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yoelDec 27 '12 at 11:05